The goal is the prevention or control of trachoma and other Chlamydia trachomatis infections of the eye. The goal is sought through better understanding of the pathogenesis, immunology and epidemiology of the infections, and through basic studies of the microorganisms. The specific aims include both clinical and laboratory studies. A long term clinical and laboratory follow-up of infants infected with C. trachomatis at birth is proposed to study the consequences of chronic infection. An exploratory study of eye infection with TWAR, an unusual chlamydia, will be undertaken. The laboratory studies will be directed at both applied diagnostic methods and more basic aspects of antigenicity, immunity and pathogenesis. They will use monoclonal antibodies and recombinant DNA techniques. Examples include: development of methods for direct staining to identify and type endemic trachoma organisms; simplification of immunotyping; antigenic analysis; production of anti-idiotypic monoclonal antibodies; application of purified antigens as vaccine; studies of neutralization of infectivity and toxicity; cloning of surface antigens and assessment of their biological role; and characterization of elementary body versus reticulate body DNA.